A Jaw-Dropping Ride, Batteries Included
Sunday, January 25, 2009
Let us begin with definitions.
First, there is the circle. It is round. It has circumference, the edge or outer limits of its roundness. It has a center and a radius, the latter being the straight-line distance from the circle's center to its circumference.
Next, there is the tangent. It is a line that touches exactly one point of a circle's circumference. That line can be an actual line; or, for purposes of this discussion, it can be the force exerted at any one point on the edge of a circle in the exact direction of the circle's rotation multiplied by the circle's radius.
Physicists and engineers call that force torque, which is best understood in automotive terms as engine twisting power and efficiency.
Torque well-delivered makes things go. You can have all the horsepower in the world. But if the energy from all of that muscle gets gobbled up and lost in the generation and transmission of twisting power, you'll have a car that goes much slower and consumes more fuel than it should.
Thus, we come to the genius and excitement of this week's test car, the Tesla Roadster. Tesla's marketers say the car delivers 100 percent torque 100 percent of the time. That's a bit of a stretch. Something always gets lost in the transmission and use of power.
But it is reasonable to agree that the Tesla Roadster delivers at least 90 percent of its torque at least 90 percent of the time, which is far better than the torque delivery of cars and trucks powered by internal combustion engines.
The Tesla Roadster is powered by batteries -- a dense pack of lithium-ion cells that feed juice to a 375-volt AC (alternating current) induction, air-cooled electric motor with variable frequency drive.
That motor, which provides the gasoline-engine equivalent of 248 horsepower and 276 foot-pounds of torque, powers the Tesla's rear wheels via a single-speed, direct-drive transmission. Judging from a day behind the wheel of the car, that speed is fast!
There are people who praise the Tesla Roadster for its environmental attributes. It consumes no fossil fuels, spews no tailpipe emissions and leaves a relatively minor carbon footprint. But all of that is missing the point, because those are also attributes of the decidedly non-sexy, campus utilitarian, golf-cart-like cars assembled by Global Electric Motorcars, a Chrysler company.
Tesla, by comparison, is a roadster's roadster. It's a head-turner, jaw-dropper. It is sexy as all get-out. And, at $109,000 a copy, it's pricey.
The Tesla Roadster deliberately eschews utility and what many motorists deem creature comforts -- such as power steering and a power-operated convertible roof. Turning the Tesla's steering wheel at low speeds requires good arm strength.
The car has seats for two people. But whoever is sitting in the passenger's seat had better buckle up and be prepared to hang on to his or her gut.
The Tesla is built for one purpose and one purpose only, which is to go as fast and as far as possible on battery power, which it does. It can run heartily for 200 miles on a single charge, after which a 3.5-hour plug-in in a washer-dryer-like 220-to-240-volt household outlet is required to restore full battery power. Slower speeds can yield a single-charge driving range of up to 240 miles.
But here's betting that no one slipping behind the steering wheel of the Tesla Roadster will be inclined to nurse it along the highway in pursuit of hyper-mileage. That is not at all what the car is about.
Would you like to know what smooth, nearly instant torque feels like? Wheeeeeee! Drive a Tesla, even if you have to fly to Tesla's Menlo Park, Calif., headquarters, to get your hands on one for a day. You will never again think horsepower is more important than torque.
Nor will you have the same tactile, emotional appreciation of automotive acceleration that marked your enjoyment of high-powered, internal combustion engines.
Wheeeeeee! If this is the future of the automobile, I want it. Let's do whatever we can to get the price down.